1. Field of the Invention
The invention relates to silicon-on-sapphire (SOS) semiconductor devices, and in particular to structures for SOS devices which operate at high operating voltages.
2. Description of the Prior Art
The typical prior art SOS semiconductor device structure consists of a silicon island on a sapphire substrate. A gate oxide is grown on the surface of the silicon island, and gate metal is deposited thereover. The thickness of the oxide at the island edge is typically only 400 A.
Although for many device applications such prior art structures are acceptable for SOS circuits with high operating voltages, such structures are disadvantageous. The relatively thin oxide thickness is a frequent source of circuit failure due to oxide breakdown.
Prior to the present invention there has not been a simple and easy-to-fabricate SOS semiconductor device structure which is relatively immune to oxide breakdown.
The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.